KR101537716B1 - Manufacturing method of scafold using centrifugation and scafold made by the same - Google Patents

Abstract

The present invention relates to a process for producing a biodegradable polymer scaffold and a biodegradable polymer scaffold prepared thereby. More particularly, the present invention relates to a biodegradable polymer scaffold which has high mechanical strength by rapidly evaporating an organic solvent using an organic solvent, And a biodegradable polymer scaffold prepared by the method.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for preparing a polymer scaffold by centrifugal separation and a polymer scaffold prepared by the method,

The present invention relates to a process for producing a polymer scaffold by centrifugation and a polymer scaffold prepared thereby, and more particularly, to a process for producing a biodegradable polymer scaffold which is rapidly and highly mechanically strong, And a biodegradable polymer scaffold prepared by the method.

Tissue engineering is an application of basic concepts and techniques of life sciences and engineering to understand the relationship between structure and function of living tissue, Or restoring it.

Recently, the field of tissue regeneration has been increasing remarkably due to the development of biomaterials and tissue engineering. A scaffolding approach to reconstructing damaged and diseased tissue has been promising in regenerative medicine. The surface chemistry and morphological effects of scaffolds play an important role not only in the initial recruitment of cells, but also their migration, subsequent differentiation and tissue formation. The ideal polymer scaffold should be made of a non-toxic biocompatible material that does not cause blood coagulation or inflammation after transplantation and should have mechanical properties sufficient to support cell growth, Which is a structure capable of successfully growing and differentiating cells due to the sufficient supply of oxygen and nutrients due to the diffusion of body fluids and the smooth formation of new blood vessels, It should take the form of a porous scaffold.

In addition, the cells are basically cultured in a two-dimensional manner. In order to cultivate them in the form of tissue or organ, a three-dimensional support is required. Such a support has numerous pores so that the cells must be able to adhere to the inside and outside of the support, and have an open structure to feed the nutrients necessary for cell growth and to discharge waste products.

Typical methods for preparing such a three-dimensional porous polymer scaffold include solvent casting / particulate leaching (SCPL), thermally induced phase separation (TIPS), microsphere sintering, electrospinning, and hydrodiesel method.

Supports made from these techniques are used for the regeneration of different tissues. It is difficult to apply a support made of one method to various tissues because the characteristics required by each organization are different. For example, electrospinning supports are applied to skin tissue or myocardial tissue, and 3D printing techniques or microsphere sintering techniques are used for the regeneration of hard bone tissue.

Such microsphere sintering is preferred for restoration of bone tissue because it has better mechanical properties and easier processing than other techniques. However, in the case of a support prepared by microsphere sintering, the degree of porosity is lower than other methods and it is difficult to increase the porosity.

In order to improve the porosity of the support, a method of replacing nonporous particles with porous particles has been studied in a method of producing a support by microsphere sintering. Recently, a method of sintering porous particles using heat . However, when the non-porous particles are sintered by heat to produce porous particles, it is difficult to control the surface porosity of the particles and the temperature of the particles increases to the glass transition temperature of the biodegradable polymer, so that the inherent characteristics of the biodegradable polymer may be changed have.

Another method of sintering particles with an organic solvent, which is another method of microsphere sintering, is a method in which a solvent for dissolving a polymer and a non-dissolvable non-solvent are mixed at an appropriate ratio to submerge the microparticles, As the surface of the particles is melted and adhered to the surrounding particles, the boiling point is lower than that of the non-solvent and evaporates more quickly. When the solvent evaporates, the particles are not melted by the non-solvent and the particles are hardly sintered.

However, in the case of the method of sintering the particles with such an organic solvent, most of the organic solvent rather blocks the pores of the particle surface, and when the time to immerse in the organic solvent is reduced so as not to block the pores of the particle surface, There is a drawback.

Disclosure of the Invention The present invention provides a method for manufacturing a polymer scaffold having high mechanical strength while solving the problems of the conventional method for preparing a polymer scaffold by microsphere sintering and reducing the immersion time of an organic solvent .

In order to solve the above problems,

Preparing polymer particles;

Preparing a mixed solvent of a solvent in which the polymer particles are dissolved and a non-soluble solvent in the non-solvent;

Mixing and dispersing the polymer particles in the mixed solvent;

Centrifuging the mixed solvent in which the polymer particles are dispersed;

Washing the remaining solvent; And

And lyophilizing the polymer scaffold.

In the method for preparing a polymer scaffold according to the present invention, in the step of preparing a mixed solvent of a solvent in which the polymer particles are dissolved and a non-solvent in which the polymer particles are not dissolved, the polymer particles are dissolved in 100 μl of the solvent for dissolving the polymer particles And the non-solvent is mixed at a rate of 20 占 퐇 to 200 占 퐇.

In the method for producing a polymer scaffold according to the present invention, the centrifugation is performed at 3000 to 10000 rpm for 1 minute to 5 minutes.

In the method for producing a polymer scaffold according to the present invention, any of the conventionally known natural or artificial biodegradable or non-degradable macromolecules which can be dissolved in a solvent to produce a porous scaffold by the freeze- Collagen, gelatin, chitosan, alginate, hyaluronic acid, dextran, poly (lactic acid), poly (glycolic acid) glycolic acid, PGA, poly (lactic-co-glycolic acid), PLGA, poly (ε-carprolactone) Poly (anhydrides), polyorthoesters, polyvinyl alcohol (PVA), poly (ethyleneglycol), polyurethane, polyacrylic acid, poly-N- Poly (N-isopropyl acrylamide), poly (Ethylene oxide) -poly (propylene oxide) -poly (ethylene oxide) -poly (propyleneoxide) -poly (ethyleneoxide) copolymer, PluronicTM), copolymers thereof or a mixture thereof . ≪ / RTI >

In the method for producing a polymer scaffold according to the present invention,

Dissolving the polymer in an organic solvent;

Dissolving the porogen in an aqueous solvent;

Dropping the porogen dissolved in the aqueous solvent into the organic solvent in which the polymer is dissolved, mixing and stirring the polymer;

Adding and stirring the mixed solution to the PVA; And

And washing the remaining PVA.

In the method for producing a polymer scaffold according to the present invention, the porogen is one or more selected from the group consisting of polyethylene glycol, F-127, NaCl, hexane, sodium carbonate, ammonium peatate and paraffin do.

In the present invention, it is preferable that the porogen is mixed with the biodegradable polymer in a weight ratio of 9: 1 to 1: 2. When the blending ratio of the biodegradable polymer and the porogen is more than 1: 2, the number of pores becomes too large and the particle strength becomes weak. When the blending ratio is less than 9: 1, have.

In the method for producing a polymer scaffold according to the present invention, the step of dropping the porogen dissolved in the aqueous solvent into the organic solvent in which the polymer is dissolved, mixing and stirring is further added with hydroxyapatite.

In the method for producing a polymer scaffold according to the present invention, the biodegradable polymer porous particles have an average particle size of 10 to 60 탆 and an average pore size of 3 to 8 탆.

The present invention also provides a biodegradable polymer scaffold prepared by the process for producing a biodegradable polymer scaffold according to the present invention.

The method for producing a biodegradable polymer scaffold according to the present invention comprises preparing a biodegradable polymer porous particle, precipitating it in an organic solvent, and centrifuging the biodegradable polymer scaffold to produce a biodegradable polymer exhibiting high mechanical strength while decreasing immersion time in an organic solvent A support can be produced.

1 and 2 show SEM photographs of porous microparticles and non-porous microparticles prepared in Examples and Comparative Examples of the present invention.
FIG. 3 is an SEM photograph of porous particles prepared by adding NaCl according to an embodiment of the present invention, FIG. 4 is an SEM photograph of porous particles prepared by adding hexane as a porogen, FIGS. 5 and 6 are cross- The SEM photographs of the porous particles prepared by the method of the present invention are shown in FIG.
FIG. 7 shows FT-IR measurement results of porous particles prepared by adding hydroxyapatite according to an embodiment of the present invention.
8 is a diagram schematically showing a manufacturing process of a support manufactured according to an embodiment of the present invention.
9 is a SEM photograph of a support prepared according to an embodiment of the present invention.
10 and 11 show SEM photographs of the support prepared in Comparative Examples 1 and 2 of the present invention.
12 to 14 are cross-sectional views illustrating a support using porous particles prepared by adding NaCl prepared according to an embodiment of the present invention, a support using porous particles prepared by adding hexane, porous particles prepared by adding hydroxyapatite SEM photograph of the support is shown.
FIG. 15 shows the results of measurement of porosity for porous microparticles and non-porous microparticles prepared according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited by the following examples.

< Example  1> Preparation of porous microparticles

< Example  1-1> As a porogen PEG If you use

As a biodegradable polymer, 300 mg of PLGA was dissolved in methylene chloride, and a solution prepared by dissolving 100 mg of PEG as a porogen in 700 μl of DI water was added dropwise to the mixture. The mixture was sonicated for 1 minute and 30 seconds using a digital ultrasonic homogenizer SONOPLUS, Output 80 %) Was used to make a primary emulsion.

The prepared emulsion was added to 100 ml of 1 wt% PVA (hereinafter referred to as 1 wt% PVA dissolved in 100 ml of DI water) and a second emulsion was prepared for 1 minute and 30 seconds using a homogenizer (POLYTRON®, 2000 rpm) made.

The prepared secondary emulsion was stirred for 4 hours at 300 rpm using a multipoint magnetic stirrer to cause methylene chloride as an organic solvent to be evaporated and PEG added as a porogen was extracted as an external water phase to prepare porous microparticles.

The microparticles were washed with 10,000 rpm centrifugal separator (SUPRA 22K, HANIL, KOREA) and ultrasonic cleaner (BRANSONIC®, Model 2510, 40kHz, Branson, USA) three times for 10 minutes.

< Example  1-2> NaCl  Is added

Porous particles were prepared in the same manner as in Example 1-1 except that NaCl was added to the inner aqueous phase.

100 mg of PEG and 0.5 mg of NaCl were dissolved in 700 μl of DI water, and 300 mg of PLGA was added to the organic phase dissolved in 3 ml of methylene chloride. The resulting solution was sonicated for 1 minute and 30 seconds using a sonicator (digital ultrasonic homogenizer, SONOPLUS, Output 80% . The first emulsion was added to 100 ml of 1 wt% PVA and a second emulsion was made using a homogenizer (POLYTRON®, 2000 rpm) for 1 minute and 30 seconds. The prepared emulsion was stirred for 12 hours at 300 rpm using a multipoint magnetic stirrer, and the evaporation of MC and the extraction of PEG and NaCl into the outer phase were carried out.

After that, PVA remaining on the surface was washed using a centrifuge (SUPRA 22K, HANIL, KOREA) and an ultrasonic cleaner (BRANSONIC®, Model 2510, 40kHz, Branson, USA) three times for 10 minutes at 10,000 rpm.

< Example  1-3> Hexane  Is added

Porous particles were prepared in the same manner as in Example 1-1 except that hexane was used as the porogen.

The hexane added as a porogen does not dissolve the biodegradable polymer but mixes well with the methylene chloride used as the organic solvent. As the boiling point of methylene chloride evaporates, the ratio of hexane to methylene chloride changes, and the PLA polymer concentration also increases. When the concentration of the polymer is increased and then it exceeds the critical point, the methylene chloride and the hexane are phase separated, and thus the organic phase in which the two organic solvents are mixed is divided into the polymer-rich portion and the deficient portion, and in this state, the evaporation of the hexaen makes the particles porous.

The internally dispersed hexane droplets become unstable and biased to one side in the internal organic phase to form the hemisphere. The large hexane droplets and the unfused small hexane droplets evaporate, creating porous hemispherical microparticles with pitted spaces and pores on the particle surface, respectively.

oil in water (O / Water) emulsion method. 1 ml of hexane was added to 9 ml of methylene carbonate dissolved in 500 mg of PLA. This solution was added to 100 ml of 0.8 wt% PVA and emulsion was made using multipoint magnetic stirrer (300 rpm). The emulsion was stirred for 12 hours in a multipoint magnetic stirrer (300 rpm) to evaporate methylene chloride (bp 39.6 ℃) and hexane (bp68.7 ℃) to prepare porous polymer particles.

The porous polymer particles thus prepared were washed with 10,000 rpm centrifugal separator (SUPRA 22K, HANIL, KOREA) and ultrasonic cleaner (BRANSONIC®, Model 2510, 40kHz, Branson, USA) three times for 10 minutes Respectively.

< Example  1-4> Hydroxyapatite  When added

Porous polymer particles were prepared in the same manner as in Example 1-1, except that hydroxyapatite was added to the organic phase.

100 mg of PEG dissolved in 700 ul of DI water was added to the organic phase in which 300 mg of PLGA was dissolved and 50 mg of HA was dispersed in 3 ml of MC, and the mixture was subjected to a first emulsion using a sonicator (digital ultrasonic homogenizer SONOPLUS, Output 80%) for 1 minute and 30 seconds made.

The first emulsion was added to 100 ml of 1wt% PVA and a second emulsion was made using a homogenizer (POLYTRON®, 2000 rpm) for 1 minute and 30 seconds.

The prepared secondary emulsion was stirred for 12 hours at 300 rpm using a multipoint magnetic stirrer to evaporate the MC and extract PEG as an external water phase. The prepared porous microparticles were cleaned with PVA remaining on the surface using a centrifuge (SUPRA 22K, HANIL, KOREA) and an ultrasonic cleaner (BRANSONIC®, Model 2510, 40kHz, Branson, USA) three times for 10 minutes at 10,000 rpm .

< Comparative Example  1> Non-porous  Preparation of microparticles

300 mg of PLGA was dissolved in 3 ml of methylene carbonate and placed in 100 ml of 1wt% PVA. The mixture was stirred for 1 minute and 30 seconds using a homogenizer (POLYTRON®, 2000 rpm), followed by oil in water (O / W) emulsion and solvent evaporation To prepare non-porous microparticles.

The prepared non-porous microparticles were washed with 10,000 rpm for 10 minutes using a centrifuge (SUPRA 22K, HANIL, KOREA) and an ultrasonic cleaner (BRANSONIC®, Model 2510, 40 kHz, Branson, USA) Respectively.

< Experimental Example  1> SEM  Photo measurement

SEM photographs of the porous microparticles and the non-porous microparticles prepared in Example 1 and Comparative Example were measured and the results are shown in FIGS. 1 and 2. FIG.

In Figure 1 (a), microparticles were prepared with 0.5 wt% PVA and porogens using PEG and 500 ul of DI water. The mean particle size was 15-20 um and the average pore size was about 3 um.

1 (b) is a microparticle prepared by using 0.5 wt% PVA and DI water of PEG and 700 ul as a porogen. The average particle size was 40-50 um and the average pore size was about 8 um.

The difference between the average particle size and the average pore size shown in FIGS. 1 (a) and 1 (b) is considered to be due to the difference in the amount of internal austenite in the organic phase. In Figures 1 (a) and 1 (b), the microparticles showed high interconnectivity and showed a slightly distorted sphere shape.

In FIG. 2, the size of the non-porous particles made of the 0.5 wt% PVA and the homogenizer manufactured at the rpm of 5,000 rpm in the comparative example was measured at 10 to 20 μm.

FIG. 3 is a SEM photograph of porous particles prepared by adding NaCl prepared in Example 1-2, and SEM photographs of porous particles prepared by adding hexane to the porogen prepared in Example 1-3 4 and SEM photographs of the porous particles prepared by adding the hydroxyapatite prepared in Example 1-4 are shown in FIGS. 5 and 6. FIG.

In FIG. 3, when NaCl was added, the mean diameter of the particles was 20 to 25 .mu.m, the average pore size of the particles was about 2 .mu.m, and the particles had good interconnectivity.

In FIG. 4, when hexane was added as a porogen, the particles did not have a spherical shape but a half-spherical hemisphere shape and the interconnectivity was not good. On one side with large hexane droplets there is almost no pore, but on the other side small pores can be seen by small hexane droplets.

5 shows an SEM image of porous microparticles prepared by adding 90 mg of hydroxyapatite to PLGA, 120 mg of (b), and 150 mg of (c). The larger the amount of hydroxyapatite added, the larger the surface porosity of the particles. It can be seen that it has a larger particle size and larger surface porosity compared to porous microparticles without hydroxyapatite, which is not only a porogen leach but also a hydroxyapatite that has been passed into the outer water phase Because. The porosity of the particles was increased due to the high interconnected structure inside, but the particles showed low intensity to break by the external force (bath sonication).

Figure 6 shows a surface SEM image of (a) microparticles with hydroxyapatite added and (b) a surface SEM image of microparticles without hydroxyapatite added. The microparticles without hydroxyapatite show a smooth surface, but the surface of microparticles with hydroxyapatite added shows that white and small grains are embedded.

< Experimental Example 2 > FT - IR  Photo measurement

The presence of hydroxyapatite in the presence of hydroxyapatite was not confirmed by the SEM image. Therefore, FT-IR was measured for the porous particles prepared by adding hydroxyapatite prepared in Example 1-4, The results are shown in Fig.

In the case of pure hydroxyapatite 1052cm ^- it represents a peak, when the pure PLGA 1750cm ^{- - 1} ₄ ² PO strong in the vicinity is known to represent a C = O peak in the vicinity of ^1. Example 1-4 The hydroxy in 7 shows the results of measurement of FT-IR pictures for the porous particles produced by adding a cross-linked apatite 1052 cm prepared ^in-the hydroxyapatite in the vicinity of ¹ PO ₄ ^{2 -} Peak 1750cm ^{- 1} was able to determine the C = O peak in the vicinity of the PLGA.

Further, FIG. The 7 larger the amount of hydroxyapatite ^1750cm-C = O peak in the vicinity of ¹ is intact, but, 1052 ^cm-hydroxy PO ₄ ² of the apatite in the vicinity of the ^1-to-peak can be confirmed that small increments . This means that as the content of hydroxyapatite added increases, the amount of hydroxyapatite contained in the particles also increases

< Example  2 > Preparation of Support

< Example  2-1>

In Example 1, 30 mg of lyophilized porous PLGA microparticle powder was dispersed in 5 ml of DI water to prepare a suspension, and 500 ul of the prepared suspension (about 30 mg of PLGA porous microparticles) was injected into a mini-column equipped with a filter Respectively. Then, air was injected and DI water was allowed to pass through the filter, leaving only the particles.

In Examples 2-1-1 to 2-1-3, the ratio of ethanol / DI water was injected into the lyophilized porous PLGA microparticle powder as shown in Table 1 below. After vortexing for 1 min, centrifugation was performed at 3000 rpm for 1 min. After centrifugation, excess DI water was injected to remove remaining ethanol and freeze-dried. The process of the above embodiment is schematically shown in Fig.

Measuring element division ethanol / DI rpm Centrifugation time Solvent / non-solvent ratio characteristics Example 2-1-1 120/180 (40%) 3000 1 minute Example 2-1-2 180/120 (60%) 3000 1 minute Example 2-1-3 240/60 (80%) 3000 1 minute During centrifugation
Characteristics according to rpm condition Example 2-2-1 180/120 (60%) 3000 1 minute Example 2-2-2 180/120 (60%) 6000 1 minute Example 2-2-3 180/120 (60%) 9000 1 minute During centrifugation
Characteristics according to time condition Example 2-3-1 180/120 (60%) 4000 1 minute Example 2-3-2 180/120 (60%) 4000 5 minutes Example 2-3-3 180/120 (60%) 4000 10 minutes

< Example  2-2>

A support was prepared in the same manner as in Example 2-1 except that centrifugation was carried out by changing the rpm at the time of centrifugation in order to evaluate the characteristics of the support according to the centrifugation conditions in the preparation of the support.

< Example  2-3>

In order to evaluate the characteristics of the support according to the centrifugation time at the time of preparing the supporter, the centrifugation time was centrifuged at 4000 rpm as shown in Table 1 above.

< Example  2-4>

In Example 1-2, support was prepared using porous particles prepared by adding NaCl.

< Example  2-5>

A support was prepared using the porous particles prepared by adding hexane in Example 1-3.

< Example  2-6>

The porous particles prepared by adding hydroxyapatite in Example 1-4 were used to prepare a support.

< Comparative Example 2 >

A support was prepared in the same manner as in Example 2-1-1 except that the non-porous microparticles prepared in Comparative Example 1 were used.

< Comparative Example 3 >

Using the porous microparticles of Example 2-1-1, ethanol / DI water was injected according to a conventional sintering method, sintered by a solvent for 6 hours under a fume hood without centrifugation, The support was lyophilized.

< Experimental Example  2 > SEM  Photo measurement

SEM photographs of the supports prepared in Examples 2-1 to 2-3 were measured and the results are shown in FIG.

FIG. 9 shows SEM photographs of the supports according to the ratio of ethanol / DI water. In Fig. 9, "a" represents Example 2-1-1, "b" represents Example 2-1-2, "c" represents Example 2-1-3, "d" represents Example 2-2-1, "e" represents Example 2-2 -2, f are the results of SEM photographs of Example 2-2-3, g is Example 2-3-1, h is Example 2-3-2, and i is the result of SEM photographs related to Example 2-3-3 to be.

In FIG. 9, as the ratio of ethanol / DI water increases, the mechanical strength of the support increases. However, as the pore size of the particle surface decreases due to the increase of ethanol, the porosity decreases.

SEM photographs of the supports prepared in Comparative Examples 1 and 2 were measured, and the results are shown in FIGS. 10 and 11.

In Fig. 10, it can be seen that when nonporous microparticles are used, the particles are simply adhered without pores on the particle surface to form a support. Also, as shown in FIG. 11, porous microparticles are used, but in the case of a support prepared according to a conventional method, most of the surfaces of the porous particles are clogged, and particles are dissolved and adhered to each other, .

< Experimental Example  3> SEM  Photo measurement

The support using the porous particles prepared by adding the NaCl prepared in Example 2-4, the support using the porous particles prepared by adding the hexane prepared in Example 2-5, the support prepared in Example 2-6 SEM photographs of the support using the porous particles prepared by adding hydroxyapatite were shown in FIGS. 12 to 14, respectively.

< Experimental Example  4> Porosity  Measure

Porosity was measured for the porous microparticles and the non-porous microparticles prepared in Example 2, and the results are shown in FIG.

15, the porosity of the supporter of Comparative Example 2 prepared by the conventional sintering method was about 23%, the porosity of the supporter of Comparative Example 3 using the porous microparticles and the centrifugation was 26% The porosity was measured to be larger than that of the comparative example in Examples 2-1-1 and 2-1-2 in which the ratio of DI water was 40% and 60%, respectively, and in Example 2-1-3, the ratio of ethanol was high As a result, the porosity was blocked and the porosity was lower than that of the comparative example.

Claims (9)

(a) dropping a porogen dissolved in an aqueous solvent into an organic solvent in which a polymer and hydroxyapatite are dissolved, mixing, and stirring to produce a primary emulsion;
(b) adding a polyvinyl alcohol (PVA) to the primary emulsion and stirring to prepare a secondary emulsion;
(c) stirring the secondary emulsion to evaporate the organic solvent, and extracting porogen and an aqueous solvent to prepare porous polymer particles;
(d) cleaning the PVA remaining on the surface of the porous polymer particle by centrifugation;
(e) preparing a porous polymer scaffold using a microparticle sintering method; And
(f) lyophilizing the porous polymer scaffold prepared by the microparticle sintering method,
Wherein the step (e) comprises: (e-1) mixing the porous polymer particles with a solvent in which the porous polymer particles are dissolved and a solvent in which the porous polymer particles are not dissolved in a volume ratio of 1: 0.4 to 1: 0.6 Administering and dispersing by stirring; And
(e-2) centrifuging the mixed solvent in which the porous polymer particles are dispersed, and washing the solvent in which the remaining porous polymer particles are dissolved.
delete The method according to claim 1,
Wherein the centrifugation is performed at 3000 to 10000 rpm for 1 minute to 5 minutes.
The method according to claim 1,
The polymer may be selected from the group consisting of collagen, gelatin, chitosan, alginate, hyaluronic acid, dextran, poly (lactic acid), polyglycolic acid poly (glycolic acid), PGA), poly (lactic-co-glycolic acid), PLGA, poly-epsilon-carprolactone, Poly (anhydrides), polyorthoesters, polyvinyl alcohols, poly (ethyleneglycol), polyurethanes, polyacrylic acid, poly-N- (Ethylene oxide) -poly (ethylene oxide) -poly (propylene oxide) -poly (ethyleneoxide) copolymer, Pluronic (poly (ethylene oxide) &Lt; / RTI &gt; TM), copolymers thereof, or mixtures thereof. The method of party support.
delete delete delete The method according to claim 1,
Wherein the porous polymer particles have an average particle size of 10 to 60 占 퐉 and an average pore size of 3 to 8 占 퐉.
A porous polymer scaffold prepared by the method of any one of claims 1, 3, 4 and 8.

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